“This is the best year of my career,” said the 10th-ranked Cibulkova, who has won two titles and appeared in three more finals. “It just feels great to be a consistent player.”

Earlier, Madison Keys advanced to the quarterfinals by defeating Misaki Doi of Japan 6-2, 6-0. Dominating throughout, the third-seeded American had five aces and avoided break points, while the 30th-ranked Doi won only 40 percent of the points on her serve.